1. Field of the Invention
The embodiment relates to a post-processing apparatus capable of performing binding as post-processing on recording media such as sheets on which an image is formed by an image forming apparatus, such as a copying machine, a facsimile, and a printer, and to an image forming apparatus including the post-processing apparatus.
2. Description of the Related Art
Widely known are post-processing apparatuses capable of performing binding as post-processing on recording media such as sheets on which an image is formed by an image forming apparatus, such as a copying machine, a facsimile, and a printer (refer to Japanese Patent No. 3658509 and Japanese Patent Application Laid-open No. H9-278258, for example). Such a post-processing apparatus may be independent of an image forming apparatus (refer to Japanese Patent No. 3658509 and Japanese Patent Application Laid-open No. H9-278258, for example), or may be included in an image forming apparatus as a part of the configuration thereof.
Post-processing apparatuses typically include a tray on which recording media passing through a section for performing post-processing are stacked.
The recording media are required to be discharged and stacked on the tray from the main body of the apparatus properly. However, if the stacking height of the recording media on the tray increases, the recording media on the tray may prevent discharge of a recording medium from the main body.
To address this, conventionally, a technology for causing the tray to descend depending on the stacking height has been developed (refer to Japanese Patent No. 3658509 and Japanese Patent Application Laid-open No. H9-278258, for example).
The stacking height will now be explained in greater detail. A recording medium may curl because of heat and pressure applied thereto while an image is being formed. In particular, if so-called side curl occurs in which both side edges of the recording medium curl upward, the stacking height increases compared with the case where the recording medium is in a planer shape. Furthermore, if the post-processing apparatus has a function to perform binding, and a bundle of recording media on which the binding is performed is stacked on the tray, a part thus bound is made bulky in the recording media. As a result, the stacking height increases compared with the case where the recording media is in a planer shape.
To discharge a recording medium from the main body properly even if the stacking height increases in this manner, an increment in the stacking height due to side curl and bulk may be added to the descent amount of the tray in the related technology.
If the tray is simply caused to descend and a recording medium is discharged thereon, however, the stacking state of the recording media on the tray may possibly be disturbed. If the descent amount of the tray is set too large, or if no side curl or bulk occurs actually, for example, the dropping amount of the recording media until the recording media are stacked on the tray increases. As a result, fluctuation occurs in the dropping direction of each recording medium, thereby increasing the possibility of the stacking state being disturbed.
Furthermore, in an assumption that binding is performed on the recording media with the recording media positioned on the tray, the binding may possibly be performed improperly if the state of the recording media is disturbed.
In other words, in the post-processing apparatus having a binding function, the state of recording media on the tray may influence the quality of the binding. Therefore, simply causing the tray to descend when recording media is discharged may possibly degrade binding performance.
There is a need to provide a post-processing apparatus capable of improving the reliability in discharging recording media onto a tray, and making the state of the recording media on the tray excellent to perform binding on the recording media properly, and an image forming apparatus, such as a copying machine, a facsimile, and a printer, including the post-processing apparatus.